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The Echo

From the Field: Mapping a Food Web

Published on January 18, 2017Written by Hernani Oliveira

My name is Hernani Fernandes Magalhães de Oliveira, I’m a PhD candidate at Queen Mary University of London and I have been working with bats for the last 12 years in the Amazon forest, Atlantic rainforest, Neotropical savannah (Cerrado), caves and the rainforests and dry forests of Costa Rica. I have mainly focused my studies on bat ecology and conservation, more specifically on the impact of deforestation on bats persistence in degraded areas and the impact of extreme climatic events such as El Niño on the interactions between bats and their food sources.

Dry forests of Area de Conservacion Guanacaste (Costa Rica) Courtesy of Hernani Fernandes Magalhães de Oliveira

According to some measures, 2015 experienced one of the strongest El Niño on records. El Niño is a climatic event that happens every 2-7 year and is expected to increase the frequency of strong events in upcoming years. It provokes changes in precipitation and temperatures around the world, causing severe droughts and floods by making some areas wetter while others drier. Costa Rica faces a very unique situation in this regard, where the dry forests of the pacific coast suffer from droughts, while the rainforests of the Caribbean coast, no more than few hundred kilometers away, experience extreme flooding. In this way, the dry forests face a decreased seasonality across the year where the rain of the wet season is dramatically decreased and the rainforests experience a sharp increase in the rainfall amount, more specifically in the wet season, resulting on an increased seasonality. These changes are important to understand, as the rainfall is usually related with fruit production and the life cycle of some insect species, thus impacting on the diet and persistence of frugivorous (fruit-eating) and insectivorous (insect-eating) vertebrates in these areas.

One of the main challenges to study food webs is the proper detection and identification of the food items present in the diet of the target species. While insectivores can almost completely digest all parts of some insect species, leaving no visible traces left behind to identify; some frugivores, when feeding on big fruits, don’t eat the seeds and leave only the digested pulp in the feces, which is equally challenging for identification. A big step forward in this way was the development of a molecular technique called DNA barcoding. DNA barcoding was developed to enable species identification based on a portion of their DNA sequence. Based on variations in the sequence of nitrogen basis of these genes, we can virtually identify any animal or plant species on the planet. So, we are using the recovered sequences from these genes found on bat feces to reconstruct the interactions between bats and their food items in more detail to better understand with a more complete picture which alterations are happening on bat food webs during El Niño years.

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